Generally, a ventilator is installed at a bathroom to ventilate an inside of the bathroom. However, even through the ventilator is operated, only internal air of the bathroom may be ventilated, but internal air in a toilet hole of a toilet may not be ventilated. Even when a user flushes the toilet after going to the bathroom, odor and germs remain and proliferate in a space inside the toilet hole. At this time, the odor and the germs inside the toilet hole spread throughout the bathroom, and contaminate air inside the bathroom. Also, the odor and the germs inside the toilet hole may spread not only throughout the bathroom, but also throughout the house, and may contaminate air throughout the house. This may cause an internal environment of the house to become unsanitary, and the old and weak or children may be infected by pathogenic bacteria.
Meanwhile, in the case of apartment houses, passages of the ventilators are connected with each other among the apartment houses, and thus when the ventilator is not operated, contaminated air may be introduced from an adjacent house into an inside through the ventilator.